Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
  • B60C11/00—Tyre tread bands; Tread patterns; Anti-skid inserts
  • B60C11/24—Wear-indicating arrangements

Definitions

• the invention relates to the field of motor vehicle tires and the detection of their level of wear. As a tire rolls on a ground, its tread that is in contact with the ground wears by friction.
• tires are commonly equipped with wear indicators.
• An example of a commonly used wear indicator consists of a rib formed at the bottom of a groove of the tire tread and whose height corresponds to the minimum depth of the grooves of the tire necessary for a correct and safe operation of the tire.
• a disadvantage of this type of wear indicator is that it requires the vigilance of the driver of the motor vehicle and a regular visual check of the condition of his tires.
• many drivers fail to perform such checks and change their tires too late, for example when during a technical inspection of the vehicle, a garage checks the state of wear of the tires.
• the object of the invention is in particular to provide a warning method concerning the wear of a simple, reliable and inexpensive tire.
• the subject of the invention is a warning method concerning the wear of a tire comprising a tread provided with at least one circumferential groove, in which: the rolling noise of the tire is measured on a tire. in the ground, one isolates, among the measured rolling noise, a noise emitted in a predetermined range of frequencies close to a predetermined frequency of resonance of a section of the groove during rolling, - the amplitude of the isolated noise is measured, compares the measured amplitude with a predetermined warning threshold.
• the method of the invention proposes to use the circumferential groove resonance properties provided on the surface of the tread of a tire.
• the part of the tire in contact with the ground is called the contact area.
• the circumferential groove section included in the contact area is covered by the ground. Thus covered, this section forms a pipe which comes into resonance due to the vibrations induced by the rolling of the tire on the ground.
• the resonance of this section causes a specific noise characterized by a frequency range centered on a resonance frequency depending on the length of the section (characteristic almost independent of the running speed) but whose amplitude changes according to the section of the pipe which itself evolves according to the wear of the tire.
• the method of the invention thus makes it possible, by measuring the amplitude of the sound produced by the resonance of the groove, to determine the wear of the tire, regardless of the type of tire used. This method is therefore particularly advantageous since it can be implemented without the need to design a particular tire.
• Another advantage of the method of the invention is that the detection is independent of the rolling speed which facilitates the noise processing algorithm and reduces its cost of implementation.
• An alerting method according to the invention may further include one or more of the following features.
• the predetermined frequency of resonance is that of a section of the groove of length substantially equal to the length of the contact area of the tire with the ground. Indeed, as mentioned above, the groove forms a pipe that comes into resonance when covered by the ground. However, the furrow is covered by the soil all along the contact area. Therefore, when the groove is covered by the ground, it forms a pipe whose length is substantially equal to the length of the contact area of the tire with the ground. Its resonance frequency is therefore substantially equal to that of a pipe whose section is equal to the groove section and whose length is equal to the length of the contact area.
• the predetermined frequency is substantially equal to C / 2L, where C is the speed of propagation of sound in the air and L is the length of the contact area.
• the first natural mode of vibration of an open pipe at both ends is such that the vibration wavelength ⁇ is equal to twice the length of the pipe, that is to say 2L .
• the frequency is equal to the speed of propagation of sound in the air divided by the wavelength, that is to say at C / 2L.
• the predetermined warning threshold is a function of an average value of the rolling noise of the tire on the ground. Indeed, the more the tire rolls at a high speed, the more the parasitic noises due to the friction of the contact area with the ground are important and the higher the average value of the rolling noise is high. It is interesting to take into account these parasitic noises to determine the value of the alert threshold and thus avoid triggering an alarm because of noise.
• the tire in the new state comprising a circumferential groove
• a wear warning is triggered when the measured resonance amplitude of the groove is below the predetermined warning threshold.
• the groove section decreases, which causes a decrease in the acoustic resonance amplitude of the groove.
• the acoustic resonance amplitude of the groove is directly proportional to the section of the pipe formed by the assembly of the groove and the ground.
• the circumferential groove causes a noise of high amplitude.
• the amplitude of this noise falls below the predetermined warning threshold, it can be considered that the section of the groove is low and this is due to pronounced wear of the tire. We can therefore trigger a wear alert.
• the tire in the new state comprising a circumferential channel embedded in the tread, said channel forming a circumferential groove when the tire is worn, a wear warning is triggered when the measured resonance amplitude of the groove is greater than the threshold. predetermined.
• the circumferential groove only appears when the tire is worn.
• this groove has the shape of a channel embedded in the tread, that is to say does not open on the outer surface of the tread.
• no furrow resonance noise appears.
• the tire is sufficiently worn for the circumferential channel opens on the tread and forms a circumferential groove, it enters into resonance, causing the appearance of a resonance noise.
• the measured groove resonance amplitude is greater than a predetermined threshold, it means that the wear of the tire is such that a groove has appeared on its surface and it is therefore time to trigger a wear warning.
• the channel has a cross section of at least 25 mm 2 .
• AF AL 1% more pipe length results in a lower resonance frequency of 1%.
• FIG. 1 schematically represents the tread of a tire according to a first embodiment embodiment, in new condition, in an axial section and the contact area of this tread with the ground
• FIG. 2 represents the tread of FIG. 1, in the worn state
• FIG. represents the tire of FIGS. 1 and 2 while driving on a ground in a radial section
• FIG. 4 schematically represents the pipe formed by the groove of the tire when it is rolling on the ground
• FIG. 5 comprises three graphs representing the rolling noise.
• Figure 6 comprises a graph representing the rolling noise of a tire comprising two if circumferentially displaced axially relative to the median plane of the tire as shown in Figure 1
• Figure 7 schematically shows the tread of a tire according to a second embodiment, in new condition, in axial section and The contact area of this tread with the ground
• Figure 8 shows the tread of the tire of Figure 4, in the worn state.
• FIG. 1 shows a tire designated by the general reference 10, according to a first embodiment, the tire 10 comprising a tread 12.
• the tread 12 comprises two circumferential grooves 14 disposed near the median plane of the tire.
• the tire 10 shown in Figure 1 is in new condition and the depth of the grooves 14 in the center of the tread is 8 millimeters.
• the tire 10 also comprises two circumferential grooves 15 disposed at the shoulders, that is to say close to the longitudinal edges of the contact area of the tread 12.
• Figure 2 shows the tire of Figure 1 in a state in which the tread 12 is worn. It can be seen that the depth of the circumferential grooves 14 and 15 is smaller than that of the grooves of the new tire. This depth in the worn state is for example equal to 2.5 millimeters.
• FIG. 3 diagrammatically shows the tire 10 traveling on a ground 16 seen in a radial section.
• the outer surface of the tread 12 is represented by a continuous line 18 and the bottom of a groove 14 or 15 is represented by a dotted line 20.
• the groove 14 but an identical description can be made in relation to the groove 15.
• the contact area of the tire 10 with the ground 16 is designated by the reference 22.
• L the length of this contact area
• the groove 14 is covered by the ground 16.
• a cavity 24 having the shape of a pipe delimited by the section of the groove 14 at the level of the contact 22 and the ground 16. This pipe opens at its two ends in and out of the contact area.
• the area of the section of the pipe 24 is substantially equal to the area of the section of the groove 14.
• the pipe 24 is shown diagrammatically in FIG. 4 in the form of a pipe of circular section and of length L equal to the length of the contact area of the tire with the ground.
• the first natural mode of resonance of the pipe 24 shown in FIG. 4 is such that its wavelength ⁇ is equal to twice the length L of this pipe.
• a dotted line inside the pipe 24 of FIG. 4 is represented as a curve representing a half-wavelength. Since the frequency is equal to the speed of propagation of the sound in the air C divided by the wavelength ⁇ , the resonant frequency of the pipe 24 is equal to C / 2L.
• this frequency does not depend on the speed of rotation of the tire on the ground and does not depend on the section of the pipe 24.
• it can have a length the contact area in the center of the order of 145 millimeters, which causes a resonant frequency of the groove 14 circumferentially substantially equal to 1170 Hertz.
• the resonant frequency is 653 Hertz.
• FIG. 5 represents three graphs, at three given speeds, of the frequency noise produced by the tire in the new state represented in FIG. 1 and by the tire in the worn state represented in FIG. 2.
• the frequency noise of the tire at the new state is shown in bold line while the frequency noise of the tire in the worn state is shown in fine line.
• the measurements were made on a BMW 3.18d vehicle in a deaf room.
• the tires are Michelin Primacy HP 205/55 R16.
• Rolling is performed on a smooth coating at the nominal inflation pressure of 2.3 bar and under rated load.
• the rolling noise is recorded by a microphone arranged in the wheel well.
• the frequency peak that appears in the case of a new tire comes from the resonance of the circumferential grooves of the tire.
• the lengths of the pipes formed by the different grooves in contact with the ground are not all identical, which implies that the resonance frequencies of the different grooves are not all the same. This is the reason why in Figure 5, the frequency peak that appears around 1200 Hz is relatively wide and not punctual.
• the method of the invention thus proposes to use these resonance properties of the circumferential grooves 14, 15 formed on the surface of the tire to trigger warnings in case of excessive wear of the tread.
• noise measured in the measured rolling noise is isolated in a predetermined range of frequencies close to a predetermined resonant frequency of a section of the groove during rolling.
• the predetermined frequency of resonance of the segment of the groove during rolling is determined to be substantially equal to C / 2L.
• the amplitude of the isolated noise is measured in this frequency range and this measured amplitude is compared with a predetermined warning threshold.
• the predetermined warning threshold is equal to the value 10. It can be seen that, when the amplitude of the noise is greater than this warning threshold, the tire is still relatively new. However, when the amplitude of the noise measured at the resonance frequency of the groove is below this alert threshold, the tire is worn and it is necessary to trigger a wear alert to inform the driver of the wear of its tires.
• this method of detecting the wear of the tire can be implemented on a tire of any type as long as it comprises at least one circumferential groove 14 whose resonant frequency can be determined simply by virtue of the length of the contact area.
• Figure 6 shows another frequency analysis of the rolling noise range centered at 1200 Hz recorded at a speed of 90 km / h. This analysis is carried out with a better resolution than that of FIG. 5. It can be seen that the peak previously described corresponds in fact to two very similar peaks. These two peaks are related to the fact that the sculpture of the tire comprises on the one hand two circumferential grooves 14 disposed near the median plane of the tire and on either side thereof and on the other hand two circumferential grooves 15 arranged shoulders, that is to say on the edges of the contact area. As indicated in FIG. 1, the contact area of such a tire is ovalized and the length of the two central grooves 14 is greater than the length of the two lateral grooves 15.
• the central grooves 14 have a length of 145 mm, which corresponds to the peak of Figure 6 visible at about 1 170 Hz; lateral grooves 15 placed at the shoulders have a length of 142 mm which corresponds to the visible peak at about 1200 Hz.
• Abnormal wear means any form of wear of the sculpture of a non-regular tire. Running in camber or a lack of parallelism between the two wheels of the same axle, or even under-inflation, may cause the appearance of such abnormal wear.
• the relative amplitude difference exceeds a predetermined warning threshold, it can trigger an alert to inform the driver that the tire has abnormal wear, non-uniform.
• FIGS. 7 and 8 show a tire 40 according to a second embodiment.
• This tire 40 comprises a tread 42 in which is embedded, in new condition, a channel 44 circumferential, as shown in Figure 7.
• a channel 44 circumferential
• An example of a design of such a tire is described in EP 1616719 It can be seen in FIG. 7 that the channel 44 is visible on the radial section of the tread 42 of the tire 40, but that this channel is invisible in the top view of the tread. Indeed, this channel 44 does not open to the surface of the tread.
• the method of the invention can be implemented either to detect the reduction of the section of a circumferential groove present on a new tire, or to detect the appearance of a circumferential groove initially embedded in the tread these two phenomena resulting from the wear of the tire.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Tires In General (AREA)

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• 2008
  • 2008-12-23 FR FR0859020A patent/FR2940190B1/fr not_active Expired - Fee Related
• 2009
  • 2009-12-21 BR BRPI0922550A patent/BRPI0922550A8/pt not_active Application Discontinuation
  • 2009-12-21 JP JP2011542874A patent/JP2012513338A/ja not_active Withdrawn
  • 2009-12-21 WO PCT/FR2009/052640 patent/WO2010072962A1/fr not_active Ceased
  • 2009-12-21 US US13/140,482 patent/US8904869B2/en not_active Expired - Fee Related
  • 2009-12-21 CN CN2009801518706A patent/CN102256813B/zh not_active Expired - Fee Related
  • 2009-12-21 EP EP09805766.4A patent/EP2379353B1/de not_active Not-in-force

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